993 research outputs found
The selective neurotoxin DSP-4 impairs the noradrenergic projections from the locus coeruleus to the inferior colliculus in rats
The inferior colliculus (IC) and the locus coeruleus (LC) are two midbrain nuclei that integrate multimodal information and play a major role in novelty detection to elicit an orienting response. Despite the reciprocal connections between these two structures, the projection pattern and target areas of the LC within the subdivisions of the rat IC are still unknown. Here, we used tract-tracing approaches combined with immunohistochemistry, densitometry, and confocal microscopy (CM) analysis to describe a projection from the LC to the IC. Biotinylated dextran amine (BDA) injections into the LC showed that the LC-IC projection is mainly ipsilateral (90%) and reaches, to a major extent, the dorsal and lateral part of the IC and the intercollicular commissure. Additionally, some LC fibers extend into the central nucleus of the IC. The neurochemical nature of this projection is noradrenergic, given that tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DBH) colocalize with the BDA-labeled fibers from the LC. To determine the total field of the LC innervations in the IC, we destroyed the LC neurons and fibers using a highly selective neurotoxin, DSP-4, and then studied the distribution and density of TH- and DBH-immunolabeled axons in the IC. In the DSP-4 treated animals, the number of axonal fibers immunolabeled for TH and DBH were deeply decreased throughout the entire rostrocaudal extent of the IC and its subdivisions compared to controls. Our densitometry results showed that the IC receives up to 97% of its noradrenergic innervations from the LC neurons and only 3% from non-coeruleus neurons. Our results also indicate that TH immunoreactivity in the IC was less impaired than the immunoreactivity for DBH after DSP-4 administration. This is consistent with the existence of an important dopaminergic projection from the substantia nigra to the IC. In conclusion, our study demonstrates and quantifies the noradrenergic projection from the LC to the IC and its subdivisions. The re-examination of the TH and DBH immunoreactivity after DSP-4 treatment provides insights into the source, extent, and topographic distribution of the LC efferent network in the IC, and hence, contributes to our understanding of the role of the noradrenaline (NA) system in auditory processing
Towards an Ashtekar formalism in eight dimensions
We investigate the possibility of extending the Ashtekar theory to eight
dimensions. Our approach relies on two notions: the octonionic structure and
the MacDowell-Mansouri formalism generalized to a spacetime of signature 1+7.
The key mathematical tool for our construction is the self-dual (antiself-dual)
four-rank fully antisymmetric octonionic tensor. Our results may be of
particular interest in connection with a possible formulation of M-theory via
matroid theory.Comment: 15 pages, Latex, minor changes, to appear in Class. Quantum Gra
Hamiltonian Noether theorem for gauge systems and two time physics
The Noether theorem for Hamiltonian constrained systems is revisited. In
particular, our review presents a novel method to show that the gauge
transformations are generated by the conserved quantities associated with the
first class constraints. We apply our results to the relativistic point
particle, to the Friedberg et al. model and, with special emphasis, to two time
physics.Comment: 20 pages, Latex, references added, the "massless" sense of (87) is
clarifie
Gravitational Duality in MacDowell-Mansouri Gauge Theory
Strong-weak duality invariance can only be defined for particular sectors of
supersymmetric Yang-Mills theories. Nevertheless, for full non-Abelian
non-supersymmetric theories, dual theories with inverted couplings, have been
found. We show that an analogous procedure allows to find the dual action to
the gauge theory of gravity constructed by the MacDowell-Mansouri model plus
the superposition of a term.Comment: 9 pages, LaTeX, no figure
Self-dual gravity and self-dual Yang-Mills in the context of Macdowell-Mansouri formalism
In this work we propose an action which unifies self-dual gravity and
self-dual Yang-Mills in the context of the Macdowell-Mansouri formalism. We
claim that such an action may be used to find the S-dual action for both
self-dual gravity and self-dual Yang-Mills.Comment: 8 pages, Revtex, no figures, submitted to Phys. Rev.
Intensity Distribution of Modes in Surface Corrugated Waveguides
Exact calculations of transmission and reflection coefficients in surface
randomly corrugated optical waveguides are presented. As the length of the
corrugated part of the waveguide increases, there is a strong preference to
forward coupling through the lowest mode. An oscillating behavior of the
enhanced backscattering as a function of the wavelength is predicted. Although
the transport is strongly non isotropic, the analysis of the probability
distributions of the transmitted waves confirms in this configuration
distributions predicted by Random Matrix Theory for volume disorder
Diseño e implementación de un sistema de detección e identificación de aficionados violentos en estadios de futbol
In this paper, we describe the design process and implementation of an avocado system to detect and identify hooligans in football stadiums. Same describing the need to implement this technology in crowded areas, is to establish a system that when combined with various technology tools, allows to have the most complete system identifier applied faces football stadiums.En este documento, se describe el proceso de diseño e implementación de un sistema avocado a la detección e identificación de aficionados violentos en estadios de futbol. Misma que describe la necesidad de implementar este tipo de tecnología en sectores concurridos, se pretende establecer un sistema que al ser combinado con diversas herramientas tecnológicas, permita tener el más completo sistema de identificador de rostros aplicado en estadios de futbol
Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)
Original research paperAnthropogenic pressures are changing the magnitude and nature of matter inputs
into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that
is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area.
In order to assess short-term responses in biomass, production, and respiration of heterotrophic
bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6
microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was
mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions
indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and
primarily limited by C in autumn. Production responded more than biomass to increasing inputs
of matter, whereas respiration did not change. The bacterial production response to increasing
dissolved organic C load associated with riverine and atmospheric inputs was strongly related to
the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that
bacterial production might decrease with the increase of P-deficient allochthonous matter inputs,
which would have important biogeochemical consequences for C cycling in coastal areas.Spanish Ministry of Science and Innovation, MINECO, CSIC, Xunta of Galicia and European Union (Marie Curie Grants)Versión del edito
Resonant radiation pressure on neutral particles in a waveguide
A theoretical analysis of electromagnetic forces on neutral particles in an
hollow waveguide is presented. We show that the effective scattering cross
section of a very small (Rayleigh) particle can be strongly modified inside a
waveguide. The coupling of the scattered dipolar field with the waveguide modes
induce a resonant enhanced backscattering state of the scatterer-guide system
close to the onset of new modes. The particle effective cross section can then
be as large as the wavelength even far from any transition resonance. As we
will show, a small particle can be strongly accelerated along the guide axis
while being highly confined in a narrow zone of the cross section of the guide.Comment: RevTeX,4 pages,3 PS figure
Remarks on 2+1 Self-dual Chern-Simons Gravity
We study 2+1 Chern-Simons gravity at the classical action level. In
particular we rederive the linear combinations of the ``standard'' and
``exotic'' Einstein actions, from the (anti) self-duality of the ``internal''
Lorentzian indices. The relation to a genuine four-dimensional (anti)self-dual
topological theory greatly facilitates the analysis and its relation to
hyperbolic three-dimensional geometry. Finally a non-abelian vector field
``dual'' action is also obtained.Comment: 16+1 pages, LaTeX file, no figures, clarifications and comments
added, typos corrected and one reference adde
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